Beginnings


	Christchurch and District Model Flying Club Sloping Off - our newsletter


	EDF IN THE CLUB - “IN THE BEGINNING THERE WAS JIM”

Jim Ruffell is a long-time member of the Club and this model of his own design was published as a plan in “Silent Flight” (although it can’t have been very silent!) in 1994. (And is still available from Sarik Hobbies, SF459 ans see below!). An article was written for Sloping Off in 1992 and there was a cartoon on the cover by the then Club member Gary John Roberts. Many thanks to archivist and the then editor Trevor for recovering it, 28 years later.

Jim’s specs for his plane are

Span approx. 36”

Flying Weight 2lb 7oz

Wing loading 22ozs/sqft

Motor - 13 turn brushed 540 with Wet magnets, approx. 30000 RPM @ 8.4V & 25A

ESC - home made MOSFET ON/OFF switch

Battery - 7 cell Sanyo Sub-C 1700SCR NICAD with ˜Power Pole” connector

EDF - homemade 5 blades, 3” or 75mm diameter fan with a 35mm dia plywood hub, PVC blades and stators, 1/64^th ply duct, approx 10 - 12ozs thrust

The power system was initially tested by strapping to a rotary washing line, achieved approx. 1.5 revs/sec, which equated to 25 mph.Maiden flight August 1992, a good hand launch required. Motor wore out brushes in approx.10 flights, new motor after 2 sets of brushes.

Plan featured in Silent Flight July 1994, placed 2^nd in scale at Hayes DMAC electric fly-in 1995.

PS: reminds of a flight at Win Green on a light air day, all going well and the fan inexplicably detonated, leaving just a faint high pitch whirr from the motor, which disappeared on shutting the throttle. Fortunately, was at height so easy dead stick landing on the top of the hill from where I’d launched. Post accident inspection revealed the motor sat in the bottom of the duct with no stators, fan with no blades and a black gooey mess around the inside of duct where the fan had been. A bumble bee strike was concluded responsible!




		The MIG 15 is a very obvious candidate for EDF (in fact PE Norman designed and built one in the ‘40s for IC ducted fan free flight, and it was Phil Smith who designed the Veron Sabre and Lavochkin - similar to the MIG - for ducted fan and also for free flight in the late ’40s). At Jim’s 36” span, a 70mm fan would fit nicely! - Ed


	Jim says “Just noticed the plan has the fan way forward, motor should be on the CG with the fan effectively sitting inside the central wing spar former. There were one or two minor points pointed out at the time (which weren’t corrected) but I missed that one.”


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